Automatic self-synchronized transmitting system



March 16, 1937. w. WATSON 7 2,074,037

AUTOMATIC SELFSSYNCHRONIZED TRANSMITTING-SYSTEM I Filed Aug. 30, 1933 ece/ber Falls/171%) INVENTOR 1 Patented Mar. 16, 1937 AUTOMATIC PATENT OFFICE SELF-SYNCHRONIZED TRANS- MITTING SYSTEM Glenn W. Watson, Detroit, Mich, assignor, by

mesne assignments, to International Business Machines Corporation, New poration of New York York, N. Y., a cor- Application August 30, 1933, Serial No. 687,438

7 Claims.

The present invention pertains to a synchronized wireless transmission system of the type described in my Patent No. 1,927,077, granted on my co-pending application Serial No. 529,436, filed April 11, 1931, and relates particularly to a means for automatically synchronizing the contact arm at the receiving end with synchronized motors at the contact arm at the wireless transmitting end, both arms being driven by approximately synchronized motors.

The object of the invention is, therefore, to, provide such a correcting means which is automatic in its operation. The system comprises, generally, transmitting and receiving disks having corresponding contacts representing characters, in conjunction with common contacts moving in synchronism over the character contacts. The actuation of a key at the wireless transmitting station makes a circuit through the common contact and corresponding character contact and sends out an impulse which, when picked up at the receiving station, causes the imprinting of the character corresponding to the character contact on the receiving disk which happens to be engaged by the associated common contact.

According to the present invention, the common movable contacts are stopped at the end of each revolution by means of electric locks. These locks however are associated with the sending keys in such a manner as to be released simultaneously on actuation of any key, whereby the movable contacts start together at the beginning of each revolution. Whatever error'in synchronism may occur in one revolution is not sufficient to introduce an error in. the reception of the signal, and the errors in synchronism are not cumulative since they are eliminated at the beginning of each revolution.

One of the principal characteristics of the invention isthat the releasing action at the receiving station is initiated by an impulse sent out from the transmitting station simultaneously with the release of the lock thereat. This impulse is distinct from the message impulse which follows when the common movable contact at the sending station engages the character contact corresponding to the previously depressed key.

The locks are under a normal tendency to extend into the paths of the common movable contacts. The lock circuits include circuit breakers each having a member carried by the movable contact. The establishment of circuits through these circuit breakers is necessary to release the locks. As soon as the movable con tacts depart from the locks, the lock-operating circuits are opened, whereupon the locking members respond to the force tending to move them into locking position. When the movable contacts return to their initial position they are retained by the locks until the latter are again released by actuation of a sending key.

The invention is fully disclosed by way of example in the following description and in the accompanying drawing, in Which Figure 1 is a diagrammatic view showing both the transmitting and receiving apparatus; and

Fig. 2 is a detail section of a modified form of contact disk.

Reference to these views will now be made by use of like characters which are employed to designate corresponding parts throughout.

For the purpose of description, the'drawing shows the apparatus adjusted for transmitting from left to right.

The transmitting apparatus, (and also the receiving apparatus) includes a conventional or modified typewriter having a series of lettered and numbered pivoted key bars I. Over the bars is mounted a roll 2 held in a slidable carriage (not shown) in the usual manner so that it is moved one space on depression of any key bar. Each key bar has associated therewith a type bar 3 adapted to strike against theroll 2 on depression of the corresponding key bar. This action is effected through a suitable linkaged between each key bar and the corresponding type bar.

A contact disk 5 carries a series of spaced contacts 6 corresponding respectively to the various characters on the type bars I. The contacts are engaged in rather rapid succession, by a rotary contact arm I carrying a sliding contact T and driven by a spring motor 8 which is in synchronism with a similar device at the receiving circuit. Obviously, the disk rather than the arm may rotate if more convenient.

Each of the key bars l is comprised in a branched condenser circuit embodying a common conductor I2 in which is comprised a condenser charging battery I3. A line i5 is extended from one side of the battery It and is branched separately to a series of contacts l6 disposed respectively beneath the key bars l and normally spaced from the latter when the bars are in their normal or raised position. The common conductor l2 extending from the other side of the battery I3, is branched at H to each of the bars I, and in each of these branches is inserted a conductor l8. Thus, when any of the bars is depressed, the corresponding branch condenser circuit will be completed at the contact i6 engaged by the depressed bar, and the corresponding condenser i8 will be charged from the battery it.

The conductor I 2 is extended to an electromagnetic coil Ifi containing a core 20, and the coil in turn is joined to the arm 1' by a conductor 2i. A radio transmitter 22 of any suitable or conventional design has its output terminals joined respectively to an antenna 23 and the ground 24. A battery 25 for operating the transmitter 22 has one of its terminals joined by a conductor 26 to one of the input terminals of the transmitter. The other terminal of the battery is joined by a conductor 2'? to a movable switch blade 28 adapted to be attracted by the core 20 when the coil I9 is energized. When the switch blade is thus attracted, it engages a contact 29 connected by a conductor 38 to the remaining input terminal of the transmitter 22.

Over each of the key bars I is a fixed contact 3| joined by a conductor 32 to the corresponding character contact 6 on the disk 5, and each key bar is thus electrically connected to the corresponding contact character 6 when the bar returns to normal position after having been depressed.

1 It may now be seen that depression of any key bar brings it into contact with the contact l6 therebeneath, thereby completing a circuit to charge the corresponding condenser from the! battery i3. When the bar is released and allowed to return to its normal position, the condenser charging circuit is broken, but a condenser-discharging circuit is completed through the corresponding contact 6, coil l9 and arm 7 when the arm engages the contact. On the occurrence of such engagement, the coil 20 is energized by the condenser, and the switch plate 28 is closed against the contact 29, thereby energizing the transmitter 22 to send out an impulse.

Adjacent the disk 5 is an automatic synchronizing device in the form of a stop or retarder comprising a coil or Winding 33 containing a sliding core 34 normally expelled by a spring 35 into the path of the arm I. Beneath each key bar is a pair of separate contacts 36 and 37, the former being joined by branch conductors 38 which lead into a line 39 connected to one side of a battery 40. The other side of the battery is joined by a conductor 4| to one of the ends of the coil 33. A series of condensers 42 have one terminal connected to the line 4|. The contacts 31 are joined by conductors 43 separately and respectively to the remaining terminals of the condensers. The lower surface of each key bar carries a contact 44 insulated as at 45 and. adapted to bridge the subjacent contacts 36 and 31 when the bar is depressed. On such movement of the bar, a circuit is completed through the battery 48 and the corresponding condenser 42 to charge said condenser.

Above each key bar are two separate contacts 46 and 41, the former being connected by conductors 48 into the corresponding or respective conductors 43 which serve to join the contacts 31 to the condensers 42. The conductors 41 are branched at 49 into a line 5!] which leads into the conductor H at a point between the coil I9 and the condensers IS. The upper surface of each key bar carries a contact piece 5| insulated as at 52 and adapted to bridge the subjacent contacts 46 and 41 when the bar is in its raised or normal position. The remaining end of the coil 33 is connected to a fixed contact 53 adapted to be engaged by a finger 54 extending from the arm I when the latter is retained by. the core 34.

It has already been explained that depression of a key bar closes a condenser circuit to charge the corresponding condenser. On release of the: bar and its return to normal position, where the contact piece 5| bridges the members 46 and 41, the corresponding condenser is discharged into the coil 33 through a circuit initiating at the condenser and comprising the conductor 4|, coil 33, contacts 53 and 54, arm 1, conductor 2|, coil l9, and conductor 50 returning to the condenser. This circuit obviously retracts the core 34, permitting the arm I to rotate, and at the same time the circuit is broken by the separation of the contacts 53 and 54, whereupon the spring 35 returns the core into the path of the arm to stop the latter at the completion of one rotation. The completion of the circuit through the coils 33 and I9 closes the transmitter circuit to deliver an impulse which however is different from and prior to the previously mentioned impulse transmitted on the engagement of the moving arm I with the contact 5 corresponding to the key bar which has been depressed.

The receiving mechanism is also in the form of a typewriter comprising key bars 6!! linked to type bars 6| adapted to strike a roll 62. Associated with the receiving mechanism is a contact disk 63 carrying character contacts 64 corresponding to the contacts 6 but of greater length in order to compensate for limited inaccuracy of synchronism during one revolution. A rotatable contact arm 65 rides. over the disk and is propelled by a spring motor 66 in substantial synchronism with the motor 8. 65 carries a sliding contact 61 adapted to move over the contacts 64.

The arm 65 however is held against rotation by means of an electro-magnetic lock such as previously described and comprising a coil 68 having a core 69 projected into the path of the arm by a spring 70. One end of the coil is connected to a fixed contact 1| engaged by a finger I2 projecting from the arm 65, when the arm is held by the core 69.

The receiving circuit further includes a receiver l3 having one of its input terminals grounded at 14 and its other input terminal connected to an antenna adapted to receive the impulses sent out from the antenna 23 in the usual manner. Also embodied in the receiving circuit is a series of mercury vapor tubes 16 here represented by two such tubes. One of the output terminals of the receiver 30 is connected by branch conductors IT to the grids 18 of the tubes and the other output terminal is connected by branch conductors 19 to the filaments 89 of the tubes.

Beneath each of the key bars 60 is a solenoid 8| adapted to operate on a plunger 82 in the form of a finger depending from the bar, so that when a given solenoid is energized by the means presently to be described, the corresponding key bar will be depressed to actuate the corresponding type bar 6|. One terminal of each solenoid 8! is joined to the corresponding contact 64 by a conductor 83. The remaining terminals of alternate solenoids 8| are joined by branch conductors 84 to the plate 85 of one of the tubes It, and the remaining terminals of the remaining or intervening solenoids 8| are:-

The arm X joined by branch conductors 86 to the plate 85 of the other tubes 16. The conductors 19 leading from the receiver 13 to the filaments 89 are joined by a conductor 81 to one side of a battery 88, the other side of which is connected by a conductor 89 to the arm 65. Finally, one of the plates 85 is connected to the remaining end of the coil 68 by means of a conductor 90.

In the operation of the device, the first impulse transmitted on return of a key bar I after depression and release thereof, that is, the starting impulse or the impulse depending on completion of a circuitthrough the coil 33 to withdraw the core 34, is received by the antenna '15 and energizes the tubes 16. Current now flows from the battery 88 through conductor 81 and one of the tubes 16, throughconductor 90, coil 68, contacts H and I2, arm 'I5,and conductor 89 returning to the battery. The arm 65 is thus released and commences its travel simultaneously with the arm 1.

When the arm 1 reaches the contact 6 corresponding to the key bar which has been depressed, another impulse is transmitted as already described and is also picked up by the antenna 15. At this instant, the arms 65 and l are in engagement with corresponding contacts 64 and 6, due to their substantial synchronization. The reception of this impulse energizing the tubes 16, completes a circuit from the battery 88, through conductor 8! and one of the tubes '16, the solenoid 8| connected to the contact 64 engaged by the arm 65, returning to the battery through the arm 65 and conductor 89. Such a circuit energizes the solenoid and actuates the corresponding key bar 69 and type bar 6| to impress the character on the roll 62.

When the arms 1 and 65 complete one revolution, they are stopped by the cores 34 and 69 40 respectively, owing to the projection of the cores into the path of the arms by means of their respective springs on breaking of the solenoid circuits as already described. The arms further start together on each revolution by the simultaneous withdrawal of the cores 34 and 69. Thus, it will be evident that the arms are brought into register or synchronism at the beginning of each revolution, so that any errors in synchronism are corrected in each revolution rather than allowed to be cumulative.

Only one of the tubes 16 is ionized at a time by a single impulse, dependent on which segment 64 of the receiving contact disk is engaged by the revolving arm 65. Each tube is operative on only a limited number of alternate character recording devices, so that the lag in a tube in circuit with a given segment 64 will not pass current through the next adjacent segment, since the latter segment at the instant of impulse was not engaged by the arm 65 and therefore did not provide a closed circuit which is necessary for ionization of the corresponding tube.

The synchronized members 8 and 66 have 65 been assumed to be spring motors, in which case they are stopped when the arms I and 65 are arrested. In order to do away with such intermittent stopping of the motors, which would be detrimental to electric motors, unless specially constructed, a construction such as shown in Figure 2 may be provided. The electric motor 9i has a contact disk 92 'fixed thereto and is provided with a shaft 93 extending through the disk. The rotary arm 94 has a frictional clutch connection with the shaft 93, consisting of a spring 95 holding the center of the armin frictional engagement with a shoulder 96 formed on the shaft. Thus, when the arm 94 is stopped, the motor continues to operate although the shoulder 96 turns relatively to the arm. When the arm is released, it turns with the shaft due to the frictional engagement between these parts. Figure 2 also shows a brush or contact member 91 which rides over contact segments 98 on the disk 92.

Although a specific embodiment of the invention has been illustrated and described, it will be understood that various alterations in the details of construction may be made without departing from the scope of the invention as indicated by the appended claims.

What I claim is:-

1. In an automatic self-synchronized transmission system, sending and receiving contact disks, a series of contacts on each disk, said contacts representing the characters, a common contact associated with each disk for selective engagement with the character contacts thereof and movable relatively thereto, substantially synchronized means tending to move said common contacts relatively to the respective disks, sending keys, a transmission circuit adapted to operate on actuation of a key and on engagement of the character contactsby the corre sponding common contacts, electric locks at said disks adapted to hold said common contacts and to release the same upon depression of a sending key, means normally tending to set =said locks to stop said common contacts in initial position, a sending circuit including a radio transmitter energized upon actuation of a key for releasing the lock at the sending disk and transmitting an impulse to simultaneously release the look at the receiving disk, and a receiving circuit in connection with said receiving disk and including a radio receiver to receive such impulse.

' 2. In an automatic self-synchronized transmission system, sending and receiving contact disks, a series of contacts on each disk, said contacts representing the characters, a common contact associated with each disk for selective engagement with the character contacts thereof and movable relatively thereto, substantially synchronized means tending to move said common contacts relatively to the respective disks, sending keys corresponding in number to the contacts on said sending disk, a transmission circuit including a radio transmitter, a battery and an electrically operated switch, said circuit being adapted to send out an impulse upon actuation of a sending key and on engagement of the character contact corresponding to said key by said common contacts, electric locks at said disks to hold said common contacts and simultaneously release'the same upon sending and receiving of said impulse, means normally tending to set said locks in looking position to stop said common contacts in normal position after operation, and circuit breakers in circuit respectively with said locks and adapted to open when said common contacts withdraw from said locks, whereby said locks return to locking position.

3. In an automatic self-synchronized trans mission system, sending and receiving contact disks, a series of contacts on each disk, said contacts representing characters, a single contact associated with each disk for selective engagement with the character contacts thereof and movable relatively thereto, the contacts on the receiving disk being longer than the contacts on the sending disk in the direction of relative movement of said single contacts and disks, stop means for said single contacts, means operated by an electrical impulse to simultaneously release said single contacts from said stops and. to permit one complete movement before again being stopped and for the purpose of synchronizing said movements, sending keys, a transmission circuit including a radio transmitter adapted to operate on actuation of a key and on engagement of a corresponding one of said character contacts by the cooperating single contact, a receiving circuit including a radio receiver, a series of receiving keys corresponding in number to the number of contacts on said receiving disk, means energized by said received impulse for operating each key, and. printing means operated by each key.

4. In an automatic self-synchronized radio transmission system, a sending circuit including a radio transmitter, a series of character keys in said circuit adapted to close said circuit and send outan impulse upon actuation of a key, a contact member having a series of character contacts, one for each of said keys and connected in said circuit, a movable contact member connected in said circuit and movable into successive contact with said character contacts, printing means operated by each key, stop means in said circuit for holding and releasingsaid movable contact member upon operation of a key, a receiving circuit including a receiver and mercury vapor tubes for stepping up received impulses, a series of character members, means in said circuit for operating each of said members upon energization of said circuit by a received impulse, a contact member having character contacts connected in circuit with said character members, means in the circuit connecting each of said character members with a corresponding character contact to operate each member upon the closing of the circuit thereof, a movable contact member connected in the receiving circuit and movable into successive contact with said character contacts, stop means in said circuit for holding said movable contact member and for releasing the same upon receipt of an impulse by said circuit, and printing means operated by each of said character members, whereby upon receipt of an impulse and the closing of the circuit of a particular character member, the character represented by that particular member will be automatically printed.

5. In a communication system, sending and receiving stations, each station having a circuitcontrol device, means to operate each of said circuit-control devices in timed relationship with that of the other, means at the sending station and included in the circuit-control device for transmitting impulses at differential times to represent different characters, each by a single impulse of the same character and additional controlling means cooperating therewith to select the timed intervals at which the single character impulses are transmitted in accordance with the different characters selected, said controlling means including means for storing the selected impulses until transmitted at the instants of time governed by the operation of said circuit-control device, means at the receiving station having recording means responsive to said transmitted impulses, said recording means being governed by the circuit controlling device of the receiver, and means whereby the selection of the character impulses to be stored at thesending station controls the circuit controlling device at the receiving station.

6. In a communication system} means to transmit character impulses including cyclically operable means for initiating the impulses at differentially timed intervals representing different characters, each by a single impulse of the same character, controlling means cooperating therewith to select the timed intervals at which the impulses are initiated in accordance with the difierent characters to be transmitted, said controlling means including means for storing the selected impulses until transmitted at the instants of time governed by the operation of said cyclically operated means, a second cyclically operable means adapted to be operated at timed relation with that of the other, means including recording means responsive to the said transmitted impulses, said recording means being governed by the said second cyclically operable means, and means to control the simultaneous release of both the cyclically operable means upon the selection of the character impulses to be stored by the said controlling means.

'7. In a communication system, means for transmitting character impulses including a normally positioned common rotary arm, normally tending to rotate, for initiating the impulses at differential times to represent different characters, each by a single differentially timed impulse of the same character, controlling means cooperating therewith to select the times at which the single character impulses are initiated in accordance with the diiferent characters to be transmitted, said controlling means including means for storing the selected impulses until transmitted at the instants of time governed by the operation of said rotary arm, character impulse receiving means including a common rotary arm, normally tending to rotate and adapted to operate in, timed relation with the first mentioned rotary arm, recording means responsive to the said transmitted impulses, .said recording means being governed by'th'e operation of the last mentioned rotary arm, and means to simultaneously release the said common rotary arms upon the selection of the character impulses to be stored by the said controlling means.

GLENN W. WATSON. 

